class_docstr: Tests MergeLayer.
      
docstr: Test the trainable_variables of the layer.
          
docstr_tok: ["Test","the","trainable_variables","of","the","layer","."]
code: def test_trainable_variables(self):
      """Test the trainable_variables of the layer."""
      layers_ = []
      layers_.append(tf.layers.Conv1D(filters=200, kernel_size=3))
      layers_.append(tf.layers.Conv1D(filters=200, kernel_size=4))
      layers_.append(tf.layers.Conv1D(filters=200, kernel_size=5))
      layers_.append(tf.layers.Dense(200))
      layers_.append(tf.layers.Dense(200))
      m_layer = layers.MergeLayer(layers_)
  
      inputs = tf.zeros([64, 16, 1024], dtype=tf.float32)
      _ = m_layer(inputs)
  
      num_vars = sum(
          [len(layer.trainable_variables) for layer in layers_]
      )
      self.assertEqual(num_vars, len(m_layer.trainable_variables))
  
imports: import numpy
  import tensorflow
  import tensorflow.contrib.rnn
  import texar.tf
  from texar.tf import context
  from texar.tf.hyperparams import HParams
  from texar.tf.core import layers
label_desc: Use image node_id 3 for calling the MergeLayerTest obj's underlying member method code with example usage: obj.test_trainable_variables() without return types